Trithiocarbonates are of commercial importance in a wide variety of applications. For instance, trithiocarbonates are used a catalysts for the preparation of dihydric phenols, in pharmaceuticals, in rubber stabilization, as ore flotation agents, as chemical intermediates, and in rapid cure adhesives. In addition to these known applications, many trithiocarbonates have proven to be of exceptional utility as control agents for free radical polymerizations.
Although there are many techniques for the preparation of both symmetrical and unsymmetrical acyclic trithiocarbonates by nucleophilic substitution (see U.S. Pat. No. 4,868,322), there are relatively few methods available for the preparation of substituted cyclic trithiocarbonate derivatives. In general, the analogous nucleophilic reactions depend on the use of 1,2-dihaloethane precursors. While useful for 1,2-dichlorethane itself, substituted derivatives such as 1-phenyl-1,2-dibromoethane are very prone to a dehydrohalogenation side reaction under the basic conditions commonly employed. This leads to low yields of the desired cyclic trithiocarbonates. More attractive as a general method for these substituted cyclic trithiocarbonates is the direct insertion of carbon disulfide into a thiirane (episulfide). While conceptually very simple, a review of the literature indicates several problems. First of all, the high reactivity and disagreeable odor of thiiranes are obstacles to the direct synthesis and use of these compounds (see M Sander, Chem. Rev., 66, 297 (1966)). Secondly, it is reported in both the patent (see U.S. Pat. No. 3,073,846) and published literature (see Y. Taguchi et. al., Bull. Chem. Soc. Jpn., 60, 727 (1987)), that the direct reaction of carbon disulfide with thiiranes requires high pressures, temperatures of 40° C. to 120° C. and “onium” or tertiary amine catalysts to obtain high yields. Needless to say, both these reaction features make this direct approach to cyclic trithiocarbonates onerous.
A recent article (J S Yadav et. al., JOC, 68, 2525 (2003)), describes the use of the hydrophobic ionic liquid [Bmim] PF6 as a novel and recyclable “solvent” for the conversion of oxiranes (epoxides) to thiiranes in an aqueous media in high yields at room temperature. This reaction can be depicted as follows:

This reaction for phenyl thiirane is virtually quantitative. The reaction is also quite general for a wide variety of epoxides. Additionally, according to Yadev et. al., there are no examples in the literature on the use of ionic liquids for the conversion of epoxides to thiiranes.